GENEVA – An international conference on Saturday accepted a U.N.-brokered peace plan that calls for the creation of a transitional government in Syria, but at Russia's insistence the compromise agreement left the door open to Syria's president being part of it.

The U.S. backed away from insisting that the plan should explicitly call for President Bashar Assad to have no role in a new Syrian government, hoping the concession would encourage Russia to put greater pressure on its longtime ally to end the violent crackdown that the opposition says has claimed more than 14,000 lives.

But even with Russia's most explicit statement of support yet for a political transition in Syria, it is far from certain that the plan will have any real effect in curbing the violence. A key phrase in the agreement requires that the transitional governing body "shall be formed on the basis of mutual consent," effectively giving the present government and the opposition veto power over each other.

Syrian opposition figures immediately rejected any notion of sharing in a transition with Assad, though the agreement also requires security force chiefs and services to have the confidence of the people. Assad's government had no immediate reaction, but he has repeatedly said his government has a responsibility to eliminate terrorists and will not accept any non-Syrian model of governance.

U.S. Secretary of State Hillary Clinton insisted on Saturday that Assad would still have to go, saying it is now "incumbent on Russia and China to show Assad the writing on the wall" and help force his departure."

"There is a credible alternative to the Assad regime," she said. "What we have done here is to strip away the fiction that he and those with blood on their hands can stay in power."

Kofi Annan was appointed the special envoy in February, and in March he submitted a six-point peace plan that he said the Assad regime accepted. It led to the April 12 cease-fire agreement that failed to hold.

Moscow had refused to back a provision that would call for Assad to step aside, insisting that outsiders cannot order a political solution for Syria and accusing the West of ignoring the darker side of the Syrian opposition. The opposition has made clear it would not take part in a government in which Assad still held power.

Russian Foreign Minister Sergey Lavrov underlined that the plan does not require Assad's ouster, saying there is "no attempt in the document to impose on the Syrian people any type of transitional process."

Lavrov accused armed opposition groups in Syria of provoking the government to use force disproportionately. "We cannot say that the regime should simply withdraw its heavy artillery that it is shooting at armed citizens," he said, referring to one of the conditions that the U.N. had set for sending truce monitors to Syria. "Certain armed groups and those who sponsor them are always trying to provoke the spiraling violence."

Chinese Foreign Minister Yang Jiechi called for all sides to end to the violence "without attaching any conditions," but said that no one from the outside can make any legitimate decisions for the Syrian people.

More than a year into the uprising, Syria's opposition is still struggling to overcome infighting and inexperience, preventing the movement from gaining the traction it needs to instill confidence in its ability to govern.

The U.N. plan calls for establishing a transitional government of national unity, with full executive powers, that could include members of Assad's government and the opposition and other groups. It would oversee the drafting of a new constitution and elections.

Annan said following the Geneva talks that "it is for the people of Syria to come to a political agreement."

"I will doubt that the Syrians who have fought so hard to have independence ... will select people with blood on their hands to lead them," he said.

The envoy had earlier warned the permanent members of the U.N. Security Council -- Britain, China, France, Russia and the United States -- that if they fail to act at the talks hosted by the United Nations at its European headquarters in Geneva, they face an international crisis of "grave severity" that could spark violence across the region and provide a new front for terrorism.

"History is a somber judge and it will judge us all harshly, if we prove incapable of taking the right path today," he said.

Syria, verging on a full-blown civil war, has endured a particularly bloody week, with up to 125 people reported killed nationwide on Thursday alone.

The opposition's divisions are tied to issues at the heart of the revolution: Whether to seek dialogue with the regime and what ideology should guide a post-Assad Syria.

Rami Abdul-Rahman, director of the Britain-based Syrian Observatory for Human Rights, said following the agreement that "no member of the Syrian opposition will accept to be part of a transitional government while Assad is still in power."

"Assad's staying in power will mean the continuation of the bloodshed in Syria," he said.

Unlike Libya's National Transitional Council, which brought together most factions fighting Moammar Gadhafi's regime and was quickly recognized by much of the international community, Syria's opposition has no leadership on the ground.

Regime opponents in Syria are a diverse group, representing the country's ideological, sectarian and generational divide. They include dissidents who spent years in prison, tech-savvy activists in their 20s, former Marxists, Islamists and Paris-based intellectuals.

Communication among those abroad and those in the country is extremely difficult. Political activists in Syria are routinely rounded up and imprisoned. Many have gone into hiding, communicating only through Skype using fake names, and the country is largely sealed off to exiled dissidents and foreign journalists.

International tensions also heightened last week after Syria shot down a Turkish warplane, leading to Turkey setting up anti-aircraft guns on its border with its neighbor.

British Foreign Secretary William Hague noted on Saturday that U.N. Secretary-General Ban Ki-moon told diplomats a U.N. monitoring mission in Syria would have to be pulled back if no diplomatic solution was found.

The head of the struggling U.N. observer mission, Norwegian Maj. Gen. Robert Mood, has described the 300 monitors approved by the U.N. Security Council to enforce a failed April cease-fire as being largely confined to bureaucratic tasks and calling Syrians by phone because of the dangers on the ground. Their mandate expires on July 20.

"Ultimately, we want to stop the bloodshed in Syria. If that comes through political dialogue, we are willing to do that," said Khalid Saleh, a spokesman for the Syrian National Council, a coalition of Syrian opposition groups based in Istanbul, Turkey. "We are not willing to negotiate (with) Mr. Assad and those who have murdered Syrians. We are not going to negotiate unless they leave Syria."

Clinton said Thursday in Riga, Latvia, that all participants in the Geneva meeting, including Russia, were on board with the transition plan. She told reporters that the invitations made clear that representatives "were coming on the basis of (Annan's) transition plan."

The United Nations says violence in the country has worsened since a cease-fire deal in April, and the bloodshed appears to be taking on dangerous sectarian overtones, with growing numbers of Syrians targeted on account of their religion. The increasing militarization of both sides in the conflict has Syria heading toward civil war.